The use of computer hard disk drives (HDD), both magnetic and optical, is well known in a wide number of computer fields, including personal computing. In computers, data is stored and retrieved from one or more disk drives by commands transmitted to the storage subsystem over a system bus.
With more particularity, a HDD has a hard disk controller (HDC), typically implemented as a chip that is mounted to a printed circuit board (PCB), with the HDC chip having connector elements (such as hemispherical structures referred to as “balls”) which electrically mate with complementary elements (such as flat pads) on the PCB. In turn, the PCB is electrically connected to the central processing unit (CPU) of a computer to communicate data between the HDD and CPU.
As recognized herein, more than a single communication interface exists and, hence, more than a single PCB connector element pattern exists. For example, it might be desirable to use a HDC with both serial interfaces such as serial ATA (“SATA”)-based PCBs and serial attached SCSI (“SAS”), and with PCBs configured for fibre channel arbitrated loop (“FCAL”) operation. SAS and FCAL are serial interfaces that have two connection “ports”, with each port having two pairs (a positive and a negative) of differential wires to support simultaneous two-way communication. Moreover, the side of the PCB on which the HDC chip is mounted can depend on the particular configuration (referred to as “form factor”) of a HDD, with the PCB connector arrangement on one side being a mirror image of the arrangement on the other side. Thus, as between the two interfaces, four possible connector element arrangements exist.
As further recognized herein, however, because SAS and FCAL are similar in that they are both serial interfaces with two ports of pairs of differential wires, it is desirable for manufacturing convenience to use a single HDC connector element arrangement with more than one PCB layout, rather than provide four different HDC chip connector element arrangements. However, as can be appreciated from the above discussion, a single HDC layout would require different electrical trace routings from the connector elements of the HDC to the various connector elements of the PCB, depending on the type of PCB and form factor of the HDD. As further recognized herein, not all trace routings are desirable. For instance, it is undesirable for the two traces connected to the two connector elements of a differential pair to be separated from each other by a large distance or to cross each other on the same plane of the PCB. It is also undesirable to have to use more than two PCB levels to avoid trace crossings. Accordingly, the challenge addressed by the present invention is to provide a single HDC connector element arrangement that can be used with four different PCB connector element arrangements without any traces crossing on the same level of the PCB and ideally without requiring the use of more than two levels of the PCB to support the traces.